The present invention minimizes or overcomes several problems associated with previous point-of-use home or office water treatment system (WTS) units. These WTS units are often connected to a faucet using a faucet diverter valve assembly. Water can be supplied directly from the faucet, or using the faucet diverter valve assembly, can be routed through a WTS unit for removal of contaminants prior to being dispensed from a faucet. The WTS units often include a carbon block filter to remove particulates, an ultraviolet (UV) bulb for destroying microorganisms found in water, and a flow meter to monitor the quantity of water treated over a specified period of time.
A first problem many WTS units encounter is that filter closures can be difficult to remove from or install on WTS unit filter housings. This is particularly true of closures that rely upon threaded connections. The closures combine with the filter housings to form closed pressure vessels in which filters are stored. The diameters of filters are ideally as large as possible to increase the capacity and life expectancy of the filters. Similarly, the diameter of filter housings must be large to accommodate the filters. Conventional threaded connections between the filter closures and filter housings, which are both usually made of plastic, often "weld" together. This phenomenon is known as galling. The "welding" action is partially attributable to the long period of time between filter changes and also to the wet and warm environment in which WTS units operate.
WTS units often include a UV (ultraviolet) bulb for destroying microorganisms in the water to be treated. These UV bulbs typically operate continuously. After water has not been run through a WTS unit for a significant period of time, such as overnight, heat from the UV bulb and other electrical circuitry can cause heat to build up inside and elevate the temperature of water stored within the WTS unit. The resulting increased temperature contributes to plastic creep and the "welding" together of the threads on the filter closure and filter housing. Because of the large area of contact between the threads, considerable force may be required to break the "weld" on the threads and release the closure from the filter housing.
Alternatively, some WTS units use bayonet mounted filter closures. A problem with this type of mount is that a filter closure must be accurately aligned with a housing to effect mounting of the filter closure to the filter housing. Also, even with a bayonet mount, there is still significant joint contact area between the filter closure and the filter housing. Again, significant force may be required to break the filter closure free from the filter housing after a long period of attachment.
A second problem associated with WTS units having UV bulbs is the build up of heat within the WTS units. Adverse consequences related to elevated temperature include structural degradation of plastic components over time due to creep, discoloration of plastic components, and decreased reliability of electrical circuitry. Also, the temperature of water stored overnight within a WTS unit can become uncomfortably warm to the touch when discharged from the WTS unit. Therefore, it is beneficial for a WTS unit to be designed to minimize its internal heat buildup.
Further, most WTS units use plastic molded decorative outer housings to enclose internal components. These plastic outer housings decrease in strength as temperature increases. If the WTS unit is to be wall mounted and must rely solely upon the strength of the outer housing, then the outer housing must be relatively thick, made of high strength plastic and resistant to creep induced by high temperatures and mechanical loads. Accordingly, expensive specialty plastics may be required in making such outer housings.
A third problem associated with WTS units having UV bulbs is that UV bulbs are cumbersome to change. The UV bulbs have a limited lifetime and must be periodically changed. While the UV light emitted by the bulbs is beneficial in destroying chemical bonds in microorganisms, hence severely inhibiting their ability to replicate or reproduce, the UV light can also be harmful to human eyes. Consequently, the UV bulbs must be mounted without UV light exposure to the installer. Often this requires numerous steps such as connecting a UV bulb to a power source, closing a housing about the UV bulb to prevent UV light exposure, and then energizing the UV bulb to insure that the UV bulb will properly operate. Ideally, a UV bulb could be easily and quickly installed with the UV bulb immediately lighting upon installation to show that it is operating properly while preventing direct exposure of the UV light to the operator.
A fourth problem common to WTS units having UV light disinfection is that water flowing through a UV tank assembly may not be uniformly treated or exposed to UV light. A UV bulb is typically mounted in a UV tank assembly with water passing around the UV bulb. All portions of the water should receive a predetermined minimal exposure or dosage of UV light. Depending on how the water is directed through the UV tank assembly, portions of the water flow receive lesser or greater amounts of exposure. That is, portions of water that pass most quickly through the UV tank assembly tend to receive less UV light exposure than portions of water that take a slower path and have a longer residence time. Ideally, all the water would receive the same predetermined minimum dosage of UV light to ensure a desired kill or destruction rate without unnecessarily overexposing certain portions of the water flow. Without steady or plug flow through the UV tank assembly, this objective cannot be optimally met. Plug flow refers to a "plug" or mass of water moving together through the system. Plug flow avoids uneven flow rate of water through the system.
Some WTS units utilize water transporting Teflon coils surrounding a UV bulb to achieve a generally uniform flow rate for all water. However, the Teflon coils can deteriorate and/or cloud over. Also, the Teflon coils can be damaged by heat. Further, water borne contaminants may reduce the transmissibility of light through the Teflon coils over time. Therefore, the coils must be cleaned or replaced in certain water conditions.
One example of a UV tank assembly that addresses this problem is shown in U.S. Pat. No. 5,536,395. A tank includes a generally cylindrical main portion and a reduced diameter neck portion. The cylindrical portion has attached thereto an inlet and a coaxially aligned annular baffle plate with circular openings therein. Water enters the inlet inducing circumferential water flow and then passes through the openings in the baffle plate. As a result, water flowing downstream from the annular baffle plate travels in a generally spiral motion about a UV bulb disposed within the UV tank assembly. The water then passes to the reduced neck portion before exiting the tank through an outlet fitting. While this UV tank assembly design provides satisfactory flow characteristics, the tank is expensive and difficult to manufacture due to numerous deep drawing operations required to form the tank. Further, there are numerous machining operations which must be performed on stainless steel components which also increases the complexity and cost of manufacture.
Another drawback conventional WTS units have is the use of a plurality of tubes to fluidly interconnect the various components of the WTS units. Individual tubes are typically used to interconnect inlets, outlets, UV subassemblies and filter subassemblies and flow monitoring devices. The large number of tubes used makes assembly inconvenient and time consuming. Further, tubes can become brittle over time and may eventually have to be replaced. With this complexity of tubes and tube clamps, replacement of parts is difficult for the average consumer. Also, as the tubes are non-structural members, additional supporting members must be used to support components such as flow meters and UV and filter subassemblies apart from support provided by decorative housings of the WTS units. Moreover, designs utilizing tubes makes optimization of the compactness of a WTS unit difficult.
The present invention includes designs and features which overcome, or at least minimize, many of the problems identified above which are encountered by previous water treatment system units.